Conrad -- is the Tek 545 the one that Jim Williams illustrates in his application notes?
I had a 535 which was ex-Grumman on Long Island. In the early 1980's Grumman, AIL, Fairchild etc. were upgrading there stuff so the scopes became available. There was a problem with arc-over on the ceramic strips -- and you didn't want to use any kind of abrasive cleanser on them.
Well, I have an HP6177B current source which has to go under the knife...
I had a 535 which was ex-Grumman on Long Island. In the early 1980's Grumman, AIL, Fairchild etc. were upgrading there stuff so the scopes became available. There was a problem with arc-over on the ceramic strips -- and you didn't want to use any kind of abrasive cleanser on them.
Well, I have an HP6177B current source which has to go under the knife...
Hi,
I do use an HP 339A, it's far better than anything else I have used to date. There must be some wiggle room to improve things a smidgen. Even going over the power supply shout help. The input BW of these things is just a bit over 1 MHz, so they do catch most of the harmonics at 100 KHz.
The older 65x oscillators could be improved. They do have a meter to read output, and those meters are deadly accurate. Also, not much wrong with a 331/2/3/4 THD meter either. They double as an accurate audio level meter, better than Leader or Kenwood and most DVMs (as mentioned). They are also better at reading THD than Leader or Kenwood. The HP does get all the harmonics, and you certainly can't say that about the newer low cost products. I feel these instruments still have a long, valuable service life, even if they can't read the lowest levels of distortion. At least the answer you get with these is the truth!
John, I may have the manual for you if you need. Probably on PDF ... I believe you can also download it from Agilent's site. The file is 7.9 M in size, so not really email friendly. Joshua, you should download the manual for normal service and alignment use.
I have repaired and restored some HP equipment over the years while working at my own shop, and also for Transcat calibration labs. The big thing is to be clean and careful, you need patience so that you don't damage the PCB. Fingerprints matter (also for Fluke and Tek). One thing you must understand is that parts suggested by the current audio fad often will degrade the performance. You need to be careful what part you use.
One thing to consider. These instruments are 30 yrs old + in many cases, at least 20 years. Often, just returning them to specification by replacing those parts that no longer work properly will buy you more than you might think. By anyone's standards, these are still excellent pieces.
Hi 1audio, Jack,
I don't know if you fellas have the time, but maybe a thread on the instruments you are familiar with to go through what you may know? I'm sure this would be a huge help to some members. Anything you can share would be helpful, but pace yourselves!
-Chris
I do use an HP 339A, it's far better than anything else I have used to date. There must be some wiggle room to improve things a smidgen. Even going over the power supply shout help. The input BW of these things is just a bit over 1 MHz, so they do catch most of the harmonics at 100 KHz.
The older 65x oscillators could be improved. They do have a meter to read output, and those meters are deadly accurate. Also, not much wrong with a 331/2/3/4 THD meter either. They double as an accurate audio level meter, better than Leader or Kenwood and most DVMs (as mentioned). They are also better at reading THD than Leader or Kenwood. The HP does get all the harmonics, and you certainly can't say that about the newer low cost products. I feel these instruments still have a long, valuable service life, even if they can't read the lowest levels of distortion. At least the answer you get with these is the truth!
John, I may have the manual for you if you need. Probably on PDF ... I believe you can also download it from Agilent's site. The file is 7.9 M in size, so not really email friendly. Joshua, you should download the manual for normal service and alignment use.
I have repaired and restored some HP equipment over the years while working at my own shop, and also for Transcat calibration labs. The big thing is to be clean and careful, you need patience so that you don't damage the PCB. Fingerprints matter (also for Fluke and Tek). One thing you must understand is that parts suggested by the current audio fad often will degrade the performance. You need to be careful what part you use.
One thing to consider. These instruments are 30 yrs old + in many cases, at least 20 years. Often, just returning them to specification by replacing those parts that no longer work properly will buy you more than you might think. By anyone's standards, these are still excellent pieces.
Hi 1audio, Jack,
I don't know if you fellas have the time, but maybe a thread on the instruments you are familiar with to go through what you may know? I'm sure this would be a huge help to some members. Anything you can share would be helpful, but pace yourselves!
-Chris
I'm on vacation now. When I get back I'll document the tweaks I have done for the Boonton 1120. I need to get another one tuned up and its a good opportunity to record the details for posterity.
"Only wimps use tape backup: _real_ men just upload their important stuff on ftp, and let the rest of the world mirror it" - Linus Torvalds, about his failing hard drive on linux.cs.helsinki.fi
"Only wimps use tape backup: _real_ men just upload their important stuff on ftp, and let the rest of the world mirror it
" - Linus Torvalds, about his failing hard drive on linux.cs.helsinki.fi
PMA, it IS possible to make certain test equipment perform better than its original specs. This is what I call BETTER. However, it is difficult to modify Tek or HP equipment in general, but perhaps the 339 can be 'hopped up' to perform as well as my ST. I improved the ST's noise by about 10dB, and perhaps 1/2'd the distortion in the oscillator. Then I use my HP3763 to lower the noise floor even further through signal averaging, and to separate the harmonic series. It is not perfect, and I am always fighting the finite 'null' that is pretty tired these days.
Still, better than -125dB is possible and probably enough, because with my design approach of minimal feedback, or just enough to meet THX specs. What I need to find is going to be there. I could care less about evaluating an AD797 or its equivalent, because I think that other factors such as PIM are more important, once you get below -110dB.
My previous concern about equipment quality, had nothing to do with most of us who actively contribute here, but AMATEURS who want to try their hand at a difficult to make (right) audio design. Live and learn PMA, give them a difficult design and they will pester you to fix it for them when it doesn't work. Perhaps you need the experience.
Still, better than -125dB is possible and probably enough, because with my design approach of minimal feedback, or just enough to meet THX specs. What I need to find is going to be there. I could care less about evaluating an AD797 or its equivalent, because I think that other factors such as PIM are more important, once you get below -110dB.
My previous concern about equipment quality, had nothing to do with most of us who actively contribute here, but AMATEURS who want to try their hand at a difficult to make (right) audio design. Live and learn PMA, give them a difficult design and they will pester you to fix it for them when it doesn't work. Perhaps you need the experience.
You know, back when I learned there was no internet. No doubt the same applies to many here. When I built a published design, like the SWTP Tiger amps, all I had was the magazine article. Maybe if you were lucky the following issue would have corrections. The really lucky might have had a mentor or more knowledgeable friends, but probably not most. The result was, you had to try a lot harder, use the library, and read whatever books on theory you could find. Persistence and patience were the keys. IMHO, today we aren't forced to develop the knack for working through a problem as much as we should be. Learning (for me anyway) isn't always easy, and sometimes being backed into a corner is a good thing. Today I can easily email just about anybody (if you're not on the 'net, you don't really exist) and it's way too easy to be lazy.
I started with building KIT's in 1959. Built a Heathkit, VTVM, Eico RF generator, Heathkit Audio generator, and Eico Cap-inductance bridge, then an Eico FM tuner.
Kits are easier and the designers GET something for their efforts, UP FRONT, without having to bail out the failures. That's a good way to go, UNLESS you have the equipment and the experience to 'do it yourself'. Later, I built an EICO oscilloscope (not easy) and a Heathkit IM Analyzer, that I completely upgraded as I built it. I used that instrument, for about 10 years.
My best efforts in audio design are virtually impossible to duplicate without lots of parts, and I mean 100's of each device, and at least $5,000 worth of test equipment. It is pointless to give people 'rope' just so the can try to hang themselves with it, and then try to bail them out of their effort.
Kits are easier and the designers GET something for their efforts, UP FRONT, without having to bail out the failures. That's a good way to go, UNLESS you have the equipment and the experience to 'do it yourself'. Later, I built an EICO oscilloscope (not easy) and a Heathkit IM Analyzer, that I completely upgraded as I built it. I used that instrument, for about 10 years.
My best efforts in audio design are virtually impossible to duplicate without lots of parts, and I mean 100's of each device, and at least $5,000 worth of test equipment. It is pointless to give people 'rope' just so the can try to hang themselves with it, and then try to bail them out of their effort.
john curl said:
Well, the first kit I built was a Remco diode receiver, followed 2 years later by a Knight "Star Roamer". So if we count the rings in the tree stump, I place my vintage at slightly less. FWIW, I did build a crystal receiver with some lead crystal (galena?) and WW-II headphones -- and I used a Quaker Oatmeal box to wrap the receing coil.
I have POOGE'd a Heath Signal Generator to the point that the only thing remaining from the original kit are the chassis, switches and meters.
My AP, on a good day with no power equipment operating, no hair dryers, no a.c operating here or anywhere between the Delaware Water Gap and Newark NJ will do -116dB.
john curl said:
Hello John
Any suggestions of improvements ?
Here is the HP333-334 service manual;
http://bama.edebris.com/download/hp/334a/hp333a_and_334a_service.pdf
Thank
Bye
Gaetan
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